Automatic signal seeking tuner



Cwrc/f Moro/Q M. A. SLAATS Filed March 6. 1961 ATTORNEYS AUTOMATIC SIGNAL SEEKING TUNER Tuzll- ./0 P4B/a Feci/wv@ Gv: ZIE M'L/,f/g/e Dg-reera@ Alan/0 Dec. 15, 1964 United States Patent O 3,161,341 AUTRMMC SiGNAL SEEKTLNG TUN Mathew A. Slaats, Livingston, NJ., assigner to Teng- Sol Eiectric line., a corporation ot Delaware Fiied Mar. 6, i961, Ser. No. 93,575 5 tCiaims. (Cl. 33e-24g This invention relates to an automatic signal seeking tuner which rotates a tuning means in a radio receiving set until a carrier wave is sensed. The invention has particular reference to improved circuit means employing a semi-conductor controlled rectier component for making such a circuit more reliable and more eicient.

Automatic tuning devices are old in the art and have been employed on many radio receiving sets, especially in those receiving sets installed in automobiles where the operator can not spend the time nor divert his attention from driving while tuning the set. Many prior art station selectors were complicated and had many circuit components including vacuum tubes and relays for operating the selector mechanism. The present invention accomplishes the same result with a minimum of components and still produces reliable operation.

One of the objects of this invention is to provide an improved automatic signal seeking tuner for radio receiving sets which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide an automatic station finder which uses fewer components, is lighter, and more reliable.

Another object of the invention is to reduce the cost of the relay used with such circuit.

Another object of the invention is to provide an automatic station selector which derives its power entirely from the twelve volt automotive storage battery.

The station selector includes a movable means for tuning the set over a predetermined band of frequencies using an electric motor and clutch with mechanical clutching means connected between the clutch and the tuning means. A twelve volt storage battery furnishes direct current power for operating the motor and the clutch, and for supplying power to the other electric components. A relay is employed for starting the motor and is operated by a manually operated switch. The relay includes an operating winding and a pair of contacts connected in series between the battery and the motor. A normally non-conducting electron discharge device having the usual anode, cathode, and control electrode is coupled to portions of the receiving set and is made conductive when a carrier wave is sensed. A solid semiconductor rectier has two of its electrodes connected across the relay winding and is controlled by the electron discharge device to short circuit the relay winding whenever the discharge is made conductive.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in connection with the accompanying drawing, of which FIG. 1 is a schematic diagram of connections of the station selector with the radio receiving circuit shown in block form;

FIG. 2 is a schematic diagram of connections showing an alternative circuit which employs a relay having only one winding.

Referring now to FIG. 1, a radio receiving circuit is indicated in block form with an antenna i1 and a ground connection 12. The receiving circuit includes the usual movable means for tuning the set (not shown) and may be a rotatable shaft having one or more variable capacitors mounted thereon. A motor and clutch 13 is connected to a twelve volt storage battery 14 in series "ice with a pair of relay contacts 15. The motor and clutch arrangement is well known in the art and is connected to the tuning means by a mechanical coupling arrangement, indicated in FIG. 1 by the dotted line 16.

The carrier wave from a radio transmitting station is sensed by coupling portions of the receiving set to the control electrode of an electron discharge device 17. Une of these coupling circuits is connected to one of the intermediate frequency transformers of the set or to the automatic volume control. This coupling circuit is connected in series with a resistor 1S which in turn is connected directly to the control electrode. The second coupling circuit to the control electrode is connected in series with a capacitor 20 and runs from the second detector anode.

The storage battery 14 is connected in series with two resistors 21 and 22, these resistors forming a voltage divider with their junction point connected to the cathode of the discharge device. The negative terminal of the battery is connected in series with another resistor 23 to the control electrode, this arrangement applying a negative bias to the discharge device and maintaining it normally in a non-conductive condition. The anode of the discharge device 1'7 is connected to the positive terminal of the twelve volt battery in series with a resistor 24 and a second pair of relay contacts 25. Since the relay contacts 25 are normally open, the anode potential is applied only when contacts 25 are closed by the operation of the relay.

The relay includes theabove mentioned normally open contacts 15 and 25, an operating winding 26 and a holding winding 27. The operating winding 26 is connected directly to the storage battery 14 in series with a manually operable switch 23 and the holding winding 27 is connected to battery 14 in series with holding contacts 25 and a small current limiting resistor Sii.

The relay is normalized by means of a silicon controlled rectifier 31 which has its anode and cathode termina-ls connected directly across the holding winding 27. The silicon controlled rectifier may be replaced by a thyratron or any semiconductor unit having thyratron characteristics. The control electrode 32 is connected to the anode of discharge device 17 and the rectiiier is made conductive by a potential applied to this electrode when the discharge device is made conductive by a combination of voltages applied to its control electrode.

The operation of this station selector is as follows: When the operator wishes to change the tuning to make the radio set bring in another station, switch 28 is olosed and thereby sends current from the storage battery, over conductor 33, through winding 26, through the switch contacts 28, and back to the negative terminal of the battery. This current ilow actuates the relay armature and closes contacts 15 and 2S. Contacts 25 are holding contacts and complete a circuit from conductor 33 through the holding winding 27 and the negative terminal of the battery, thereby holding the armature in its actuated condition until winding 27 is later short-circuited by rectier 31. When contacts 15 are closed, the motor 13 is started and the clutch associated with the motor is energized to transmit motion to the tuning means in the radio set. The tuning is then varied slowly over the predetermined band of frequencies.

As soon as a carrier wave is sensed through components 18 and 20, the voltage of the control electrode in dischange device 17 is raised and the discharge device is made conductive so that current iiows from the postive terminal of battery 1d, over conductor 33, through contacts 25 and resistor 3h, through resistor 24 to the anode-cathode electrodes in the discharge device, through resistor 22 and back to the negative terminal of the battery. This current ow reduces the potential of the anode in discharge device l? and applies a triggering potential to electrode 32 thereby 'causing rectifier 3l to conduct and short circuit the current through the holding winding 2-7. As lsoon as this occurs the relay aramture is normalized, contacts are opened and the clutch and motor are normalized, thereby stopping the movement of the tuning means and retaining the radio set in a condition for receiving the sensed carrier wave.

If the operator desires to retune the set to bring in another station, switch 23 is again closed and current will then flow through winding 26 to actuate the relay, It will be noted that this action actuates the relay regardless of the condition of rectier 3l and the current through winding 27.

Referring now to FIG. 2, the clutch and motor combination 13 are connected as in FIG. 1 between the storage battery 14 and contacts l5. The manually operable switch 28 is connected between the negative side or ybattery 14 and a single winding 34 on the relay. This circuit includes a limiting resistor' 35. The controlled rectifier 31 is connected across the relay winding 34. When switch 2S is closed, the relay is actuated by current which flows from the battery 14 through resistor 35, winding 34, switch 2S, and back to the negative side of the battery. The relay armature is held in its actuated condition by a holding circuit which can be traced from the position battery terminal through resistor 35, through winding 34, closed contacts 38, through a current limiting resistor 36, through holding contacts 37, and back to the negative terminal of the battery. When a carrier wave is sensed and the controlled rectiier 31 is made conductive, the winding 34 is shortcira cuited and the relay armature tis normalized, thereby stopping the motor and normalizing the clutch in the manner described above. When the operator desires to change from one station to another, switch 28 is again closed and the relay armature is actuated to start the motor. The operation of switch Z n'ot only sends current through winding 34 but also disconnects, by opening contacts 38, the connection from the cathode of rectier 31 to winding 34 thereby permitting current to ow through the winding even though a strong carrier wave is being sensed by the discharge device 17.

From the above description it will be evident that the invention provides a dependable and eicient automatic tuner for radio receiving sets with only one yvacuum tube and a minimum or" circuit components.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to `be interpreted in a limiting sense. The only limitations are to be determined from the scope of the appended claims. f

l claim:

l. An automatic signal seeking tuner for a radio receiving set comprising: a movable means for tuning the set over a predetermined band of frequencies; an electric motor and clutch with coupling means between the clutch and said movable means for changing the tuning; a source of electric power for driving the motor; a relay having a winding which is connected to the power source by a manually operable switch and a pair of contacts connected in series between the source of power and the motor; a semiconductor switching device having two electrodes connected across said relay winding; a normally non-conducting electron discharge device having an anode, a cathode, and a control electrode for sensing the presence of a carrier wave in said set; circuit coupling means between portions of said set and the control electrode for rendering the discharge device conductive when a carrier wave is sensed, and circuit coupling means between the anode and the switching device for short circuiting the relay winding and normalizing the relay when current flows through the electron discharge device.

2. An automatic signal seeking tuner as set forth in claim 1 wherein said source of electric power is a direct current storage battery.

3. An automatic signal seeking tuner as set forth in claim l wherein said switching device is a controlled rectifier having an anode, a cathode, and a control electrode.

4. An automatic signal seeking tuner as set forth in claim 3 wherein said relay is provided with a holding circuit and holding contacts for locking the contacts into clos-ed condition when the relay is actuated by the manual switch.

5. An automatic signal seeking tuner for a radio receiving set comprising: a movable means secured to a tuning shaft for tuning the set over a predetermined band of frequencies; an electric motor and clutch with coupling means between the clutch and the tuning shaft for changing the tuning; a storage battery for driving the motor; a relay having a iirst operating winding connected in series with the battery and a manually operable switch for actuating the relay and starting the motor; a second winding for holding the relay contacts in their closed position after the relay has been actuated; a silicon controlled rectiiier having an anode and a cathode connected across the second relay winding, said silicon controlled rectiiier having a control electrode; a normally non-conducting electron discharge device having an anode, a cathode, and a control electrode for sensing the presence of a carrier wave in the receiving set; circuit coupling means between portions of said receiving set and the control electrode of the discharge device for rendering the discharge device conductive when a carrier wave is sensed; and circuit coupling means between the anode of the discharge device and the control electrode of the rectifier for short-circuiting the second relay winding and normalizing the relay when current flows through the anode-cathode circuit of the electron discharge device.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. AN AUTOMATIC SIGNAL SEEKING TUNER FOR A RADIO RECEIVING SET COMPRISING: A MOVABLE MEANS FOR TUNING THE SET OVER A PREDETERMINED BAND OF FREQUENCIES; AN ELECTRIC MOTOR AND CLUTCH WITH COUPLING MEANS BETWEEN THE CLUTCH AND SAID MOVABLE MEANS FOR CHANGING THE TUNING; A SOURCE OF ELECTRIC POWER FOR DRIVING THE MOTOR; A RELAY HAVING A WINDING WHICH IS CONNECTED TO THE POWER SOURCE BY A MANUALLY OPERABLE SWITCH AND A PAIR OF CONTACTS CONNECTED IN SERIES BETWEEN THE SOURCE OF POWER AND THE MOTOR; A SEMICONDUCTOR SWITCHING DEVICE HAVING TWO ELECTRODES CONNECTED ACROSS SAID RELAY WINDING; A NORMALLY NON-CONDUCTING ELECTRON DISCHARGE DEVICE HAVING AN ANODE, A CATHODE, AND A CONTROL ELECTRODE FOR SENSING THE PRESENCE OF A CARRIER WAVE IN SAID SET; CIRCUIT COUPLING MEANS BETWEEN PORTIONS OF SAID SET AND THE CONTROL ELECTRODE FOR RENDERING THE DISCHARGE DEVICE CONDUCTIVE WHEN A CARRIER WAVE IS SENSED, AND CIRCUIT COUPLING MEANS BETWEEN THE ANODE AND THE SWITCHING DEVICE FOR SHORT CIRCUITING THE RELAY WINDING AND NORMALIZING THE RELAY WHEN CURRENT FLOWS THROUGH THE ELECTRON DISCHARGE DEVICE. 